Obesity remains a major health problem in US and causes metabolic complications such as diabetes, dyslipidemia and insulin resistance. Similar complications also occur in patients with familial lipodystrophies characterized by partial (familil partial lipodystrophy, FPL) or almost complete (congenital generalized lipodystrophy, CGL) lack of body fat. In the last few years, several genes for CGL (AGPAT2, BSCL2, CAV1 and PTRF); FPL (LMNA, PPARG, AKT2, CIDEC and PLIN1); mandibuloacral dysplasia (MAD; LMNA and ZMPSTE24); autoinflammatory (PSMB8); SHORT syndrome (short stature, hyperextensibility/hernias, ocular depression, Rieger anomaly and teething delay; PIK3R1); and MDP (mandibular hypoplasia, deafness and progeroid features) syndrome (POLD1) associated lipodystrophies have been identified. However, affected subjects from approximately 200 pedigrees with CGL, MAD and especially FPL lack mutations in these genes suggesting additional loci. Furthermore, the genetic basis of many extremely rare varieties of lipodystrophies associated with SHORT and neonatal progeroid syndromes remains unknown. Thus, the first aim of this proposal is to identify additional gene(s) involved in adipocyte biolog, development and differentiation that cause lipodystrophies and to determine their function in adipocyte biology. We will use state-of-the-art whole exome sequencing to identify the molecular defects in these families. The second aim is to ascertain relationships between molecular defects in lipodystrophy genes with metabolic derangements using well-phenotyped probands, families, and populations. These studies will unravel molecular mechanisms involved in causation of lipodystrophy, and insulin resistance and its associated morbidities. This new knowledge may provide targets for developing novel drugs for treating diabetes, dyslipidemias and hepatic steatosis.